The tail light is, overall a very good product. It features 36 led mini lights arranged in 4x9 array and has 7 different modes. The light intensity goes from very bright to bright, even in the low intensity settings. Even on a bright, sunny day one its low intensity settings, the "econ" blinking display is very bright and according to the specs, will last 20h. I have yet to test the longevity of the battery, but given my experience with other Nite Ride lights, I expect that the listed specifications are close to reality.
A rating of 4/5 starts due to one negative: the light holding strap has significant limitations of attaching this light to your bike. It's sturdy but the only place where this strap will fit well is around a round seat post. The strap is also useless for being fixed to seat stays, which on most bikes have small diameter.
Best use: take the light out of the strap holder and hook it onto your saddle bag if it has a light attachment strap.